Enthalpies of transfer of aliphatic compounds from vapor to solvents. Steric hindrance to functional group solvation

Enthalpies of transfer from the vapor to solution (ΔH(v → S)) in cyclohexane are similar for alkenes and the corresponding alkanes. The transfer from vapor to dimethylformamide is about 0.6 kcal/mol more exothermic for 1-alkenes, which results from the dipole-induced dipole interaction of the solvent dipole with the π system. When the ethylenic bond is hindered by large adjacent groups (trans-1,2-di-tert-butylethylene) to the approach of solvent dipoles, ΔH(v → DMF) becomes similar to that of the corresponding alkane (1,2-di-tert-butylethane). Similarly the interaction of di-tert-butyl ketone with DMF is 0.7 kcal/mol weaker than that of the less hindered isomer, 2-nonanone.